Mycosphaerella is a bottleneck in cucumber cultivation. Because this fungus leaves most crops untouched, growers primarily use resources that have been developed to combat mildew. Researcher Jantineke Hofland-Zijlstra of Wageningen UR Greenhouse Horticulture advocates a multi-pronged approach.

Mycosphaerella likes high humidity and feels right at home in greenhouses. The fungus is a major threat to cucumber, especially since only a limited number of fungicides have sufficient effect. Rocket is one of the mildew agents that also works well on this fungus. In addition to research on (new) mildew agents, products are also screened for Mycosphaerella.

Three symptoms
Relying on chemical control alone provides insufficient protection in the long term, says researcher Jantineke Hofland. "Mycosphaerella affects cucumber plants in different ways. Depending on the part of the plant, we see different symptoms."

Leaf Infection is recognizable by the yellow dots on the leaves, followed by a characteristic V-shaped pattern along the margins. Stem Infection generally occurs at the base of the plant, where there are black, spores-containing spots. The third symptom is fruit rot, with a prominent constriction at the end of the fruit.

System approach needed
Wageningen UR is pursuing a multi-faceted approach, based on increased resilience of the plant, the use of natural antagonists, climate control, and - as a last resort - corrective measures that prevent the germination of spores.

Hofland: "We are working on several projects. For a good preventive effect against fungi, it is important that an agent reaches the flower prematurely. Together with LTO Glaskracht Nederland and suppliers of pollinators, we want to do research on biological antagonists.

Measurement sets

"We have already developed test kits to record the effect on the plant," adds Hofland. "This can be done by measuring concentrations of salicylic acid and jasmonic acid in the plant. Either way, an integrated approach is necessary to stay ahead of Mycosphaerella.”

Source: Certis Magazine Glashelder.

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